Development of a dense wavelength division multiplexing (DWDM) technology has resulted in a continuous increase in an information transmission speed and capacity in an optical fiber communications link, and resulted in an increase in requirements for an information exchange speed and capacity in an optical communications network (for example, a metropolitan area network or a data center). An all-optical switching system becomes a development trend in the optical communications network. An optical switch is a key device for implementing the all-optical switching system. The optical switch may implement functions such as route selection, wavelength selection, optical cross-connection, and self-healing protection of an all-optical layer. Currently, an optical switch mainly includes a conventional mechanical optical switch, a micro-electro-mechanical system (MMEMS) optical switch, a liquid crystal optical switch, a waveguide optical switch, a semiconductor optical amplifier optical switch, and the like.
A conventional MEMS optical switch is usually based on an electrostatic-actuation micro reflector structure, has advantages such as a low insertion loss, low crosstalk, a high extinction ratio, good scalability, and simple control, and may have at least 1000 ports in scale. However, because a rotation speed of a micro reflector is low, a switching speed of this type of optical switch usually can reach only a millisecond level. Consequently, a requirement for a future microsecond-level switch speed cannot be met. Because a process of a silicon-based waveguide optical switch is compatible with a mature complementary metal oxide semiconductor (CMOS) process, the silicon-based waveguide optical switch has advantages such as low costs and high integration, and it is easy to implement a large-scale optical switch matrix. A switching speed of the optical switch may reach a microsecond level by using a thermo-optic effect of silicon materials. However, the thermo-optic effect of silicon materials is relatively weak, and a refractive index changes slightly. Therefore, a Mach-Zehnder interferometer (MZI) structure needs to be used to implement a 1×2 or 2×2 optical switch. The large-scale optical switch matrix is formed by cascading optical switches. The optical switch of the MZI structure has a noticeable loss in both a drop state and a through state, and the loss increases rapidly with an increase in dimensions of the optical switch matrix. The silicon-based waveguide optical switch has a problem of a high insertion loss, and this limits application of the silicon-based waveguide optical switch.
Therefore, implementing the optical switch matrix with a microsecond-level switching speed, a low insertion loss, a large quantity of ports, and low costs is an important part of future development of an all-optical switching technology.